This invention relates to a discharge valve and valve seat for a reciprocating compressor wherein the area inward of the valve seat is significantly larger than the area of the port leading to the discharge valve.
Reciprocating compressors typically include a piston movable within a cylinder. A valve plate at one end of the cylinder selectively allows a fluid to be compressed to flow into the cylinder through an inlet valve. The valve plate also includes a discharge valve to control the flow of the compressed fluid outwardly of the cylinder. In one common arrangement of the valve plate, the inlet valve is positioned at a radially outer location on the cylinder, while the discharge valve is positioned at a central location. The discharge valve is on an outer surface of the valve plate. A discharge port leads through the valve plate to the discharge valve. Typically, the discharge valve seats against a valve seat on the valve plate. The valve seat has typically surrounded the discharge port, such that an area defined inward of the valve seat is equal to or slightly larger than the area of the discharge port.
There are trade-offs in the design of the discharge valve for such compressors. In particular, the area of the discharge port is proportional to a quantity known as “flow loss.” Flow loss represents a decrease in efficiency in that it represents fluid which has been compressed but which is not driven outwardly of the cylinder to a downstream use. That is, fluid in the discharge port at the time the piston reaches the end of its stroke is not driven further outwardly of the discharge valve. All of the energy put into this compressed fluid is “lost.” For this reason, it is not beneficial to excessively increase the size of the discharge port.
On the other hand, it is the area within the valve seat that controls the amount of force applied from the compressed fluid to open the discharge valve and allow flow of the fluid outward of the chamber. In certain applications, it would be desirable to increase this force without dramatically increasing the pressure of the compressed fluid.
To date, the designers of reciprocating compressors have chosen some relative equal value for the area within the valve seat and the area of the discharge port based upon an evaluation of the applications to which the reciprocating compressor will be utilized. In fact, since many compressors are utilized across a wide range of operational applications, this trade off may not always be as beneficial as would be desired. The problem becomes particularly acute when an unique refrigerant such as CO2 is utilized in a refrigerant cycle.